Heat-treatment apparatus



Dec. 22, 1953 J, A. REDMOND HEAT-TREATMENT APPARATUS Filed Aug. 12, 1950 INVENTOR John A Redmond.

' TTORNEY WITNESSES: 54W%4% Patented Dec. 22, 1953 2,663,789 HEAT-TREATMENT APPARATUS John A. Redmond, Baltimore, Md., assignor to Westinghouse Electric, Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 12, 1950, Serial N 0. 179,077

2 Claims. 1

This invention relates to multiple frequency heat-treatment systems, and in particular to the arrangement of heating units therein.

The apparatus of the prior art, of which I am aware, has the limitation that it is necessary to heat-treat at one time gears having one size only. For a manufacturer of automotive equipment who utilizes a mass-production conveyor system and requires for it several sizes of gears, it is necessary to stock-pile heat-treated gears of one size while gears of another size are being heat-treated. The only way to provide heat-treated gears at the necessary relatively continuous rate with the heat-treatment apparatus of the prior art is to heat-treat gears of each desired size in greater quantities than the production assembly line would require during the periods necessary to individually heat-treat gears of all other required sizes.

According to teaching of other prior art with which I am familiar, the necessary continuous flow of heat-treated gears in all required sizes can be maintained by providing an individual heat-treating apparatus for each such desired gear size. For example, if an automobile manufacturer requires five different sized gears in an automobile transmission, he could set up a separate heat-treatment apparatus for each of the five gear sizes, and feed the output from each heat-treatment apparatus directly to the automotive transmission assembly line.

Both expedients, while useful for many purposes, sometimes involve excessive cost in installation, maintenance and operation.

It is, accordingly, an object of this invention to provide heat-treatment apparatus which will not require the stock piling of heat-treated gears of one size, while said apparatus is heat-treating another sized gear.

Another object of my invention is to provide a single heat-treatment apparatus wherein metallic objects, such as gears, having different physical dimensions can be readily heat-treated.

A further object of my invention is to provide apparatus having a plurality of heating units for the high frequency heat-treatment of metallic objects, which can be supplied power from a single high-frequency source without requiring cumbersome and expensive high-frequency switches.

-Still another object is to provide apparatus which will heat-treat gears of various dimensions from a single high-frequency power supply without high-frequency switching.

A still further object is to provide a heat-treatment system wherein diiierent sized gears may be heat-treated at a substantially continuous rate, or as may be required in normal mass-production automotive assembly lines.

An ancillary object of the invention is to minimize the loading effect of an empty induction heating unit in the high-frequency arrangement thereof.

A further ancillary object is to make the impedances of the empty high-frequency inductor coils relatively high as compared to the impedance of the inductor coil in which a metallic gear is being heat-treated.

In accordance with this invention, a first plurality of induction heating coils are provided for the low frequency preheating of metallic gears. A second plurality of induction heating coils, corresponding in number to said low frequency induction heating coils, is supplied with high-frequency current and provided to harden said metallic gears. The high-frequency coils are connected in parallel, and all are supplied power from a common high-frequency source. For each sized gear to be heat-treated, a low-frequency heating coil and a corresponding high-frequency heating coil is provided. The low-frequency heating coils can be supplied from suitable separate power sources, or they can be supplied from respective individual secondary windings fed from a common primary winding. A given metallic gear is first preheated by the low frequency energy un-' til it reaches a desired temperature and metallic condition. Then said gear is transferred to the corresponding high-frequency heating coil where a high-frequency current is applied to heat said gear to the desired temperature for proper hardness. In general, the necessary low frequency treatment requires an appreciably longer period of time than the high frequency treatment. The gear can then be removed from the high-frequency coil, and given the necessary quench treatment.

At any given instance of time, it is better if only one of the high-frequency induction heating coils has a gear'in it undergoing heat-treatment. The

remaining parallel-connected high-frequency inmay have different dimensions for the heat-treatment of respectively different sized gears. To

minimize the power drain of the remaining empty.

high-frequency induction coils, a powdered iron core may be positioned within said empty coils.

3 This decreases the loading or the power drain of the empty coils in such a manner that more of the available power can be utilized by the loaded coil.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its methed or operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

The figure shows a multiple ireeaency hea't treatment system in which the highinduction coils are connected parallel to a single source of high-frequency energy; 7

In the figure is shown a multiple frequency heating'treatment is completed, the gear 40 is transi r red to the corresponding high-frequency induction coil 18 where it is given a hardening treatment by the application of high-frequency energy for a predetermined period of time. The

heat-treatment apparatus in which a. plurality of high-frequency induction coils l0, l2, I4 and IS are parallel connected to a single source transmission line it of suitable high-;frequency power. All of said high-frequency inductor coils 1-8, l2, l4 and it may be adapted for the treatment of the same sized gear, or each of them may be designed to treat a diiie'ren't sized gear. The choice of inductor coil size is determined primarily by the relative requirements ior the different sizedxgears to be heat-treated A plurality or low ireauency induction heat eoils it, 22, a l and 26. is shown. The latter coils 28, 2 2., as and 26 are positioned adjacent the corresponding highfreq-ue ncy coils in, ii, 1 4 and 5 53.. respectively, so a given gear can be preheated by a lowfrequency coil and moved into the corresponding h-i'gh frequency coil for hardening treatment. Each of "said low ire'quency coils 2Q, 22, 24 and as can be supplied power from respective individual Ipower supplies, or they can be supplied energy from a single low-frequency power source through "a transformer 35 having one primary winding '38 and a secondary winding 28, 35, 3-2 and $4 for each of said low ireqnency coils. Positioned to be inserted into one of the ar frequency induction coils l5 there is shown a metallic :gear '49 positioned for heat-treatment. Near each of the other high=irequency induction coils 11]., I 2 and V4 there is shown :a powde'red iron core 42., M and #16, respectively. the practice of my invention, a metallic gear is generally heat treated in only one 0f the highfrequency in'duaion coils at a :given time, unless there is s-uiiici'ent power available to handle more than one loaded Coil.

The heat=treatment apparatus shown in the figure operates to apply a irnultipl'e frequency pair of neat-treatment Coils, fii example, @6113 lo and 20. The n'ei'rt larger gear the second air-or neat-treated eoils l 2 and 22-, the third larger gear in the next pair oi h'eat tre'atrnent coils l4 and 2 4', and the largest gear in the last pair of heat treatment coils it and :25.

The 'heat 'treatment operation "at each "or said pairs of heat-treatment polls is, general, the

time duration of the hardening treatment similarly depends upon several factors such as the hardness desired, the depth of penetration of the hardness, and the pitch and width of the gear.

high-frequency induction coils l6, 12, M or 16 is generally heat-treating a gear at any given: This allows the available .p'ower to foe time. supplied from a smaller power source, than it were not at this one stage of heat-treatment.

The empty parallel connected .iiig'h :i-iequ'eney' coils are no problem as they present relatively.

m n impedance to the whole circuit. The load ing effect of the remaining empty high-frequency.

induction cells, which results in 'a decrease of power available at the one stage that is heattreating a gear, can be reduced however by zin setting a suitable powdered iron core 42, ii'ser ie within each for the empty cells 4 8, 1'2 $4. The impedance of the coil having :a gear in it is much lower than the impedance of any empty coil, but the powdered iron core in each empty cell further increases its relative impedance to correspondingly decrease loading eire'ct there:-

Although I have shown and described certain specific embodiments of my invention, 1 ainifully. aware that ma ny modifications thereof are pos restricted except insofar as necessitated by the prior aftafld by the spirit the ap ended I Claim '35 my ihVenti n:

1. In apparatus for the heat tie'a or a reg i'ilai' metallic objects, the ion iii 'a first plurality or inflection heating units can: to a suit is nected in nasal: and con ed source or e ueney current, a second plw rarity or induction nea tmg corresponding in rrumber and respective dimensions to said first plurality of induction heating each oi the second plurality of induction heating "units being connected to a source or low-frequency (current, and a plurality of core members corresponding in :iiuniber to all but one or sai'd'ifirst plurality.

first plurality of induction heating units eonnect'ed in vparallel and being connected to a suitable source of high-frequency current, a second plurality of induction heating units corresponding' in number and respective dimensions to said In our practical operation, only one of first plurality of induction heating units, each of the second plurality of heating units being connected to a source of low-frequency current, said first and second plurality of heating units respectively having different dimensions for the heat treatment of difierent-sized metallic gears, and a plurality of powdered iron core members corresponding in number to all but one of said first plurality of heating units and positioned respectively to occupy the latter heating units other than said one during a heat treatment time interval when the latter heating units other than said one do not contain metallic objects undergoing heat treatment.

JOHN A. REDMOND.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Smith Mar. 5, 1935 Denneen et al. Aug. 1, 1939 Denneen et al Feb. 3, 1942 Dravneek July 11, 1944 Jordan June 29, 1948 Mittelmann Nov. 9, 1948 Wood May 31, 1949 Bachman June 13, 1950 FOREIGN PATENTS Country Date Great Britain Aug. 8, 1947 

